Total parenteral nutrition has been used infrequently during pregnancy. Because of the special nutritional needs and hormonal environment of the maternal-fetal unit, there is uncertainty as to the optimal composition and quantity of total parenteral nutrition therapy. In this report two important questions are examined: whether or not a protein replacement commonly used in total parenteral nutrition provides adequate levels of essential amino acids to fetus and mother, and whether or not the daily use of fat emulsion as part of total parenteral nutrition is associated with unwanted side effects. The authors' data suggest that certain adjustments have to be made in the quantity and composition of total parenteral nutrition constituents to provide the necessary nutritional requirements for metabolic and anabolic needs without increasing the overall risk for complications.